1. Field of the Invention
The present invention relates to a photoconductor for electrophotography, and more particularly to a photoconductor for electrophotography which includes an electroconductive substrate having laminated thereon a subbing layer and a photosensitive layer in this order.
2. Description of Prior Art
Recently, as photoconductors for electrophotography (hereafter, sometimes referred to simply as "photoconductors") for use in copiers or printers utilizing an electrophotographic system, those photoconductors which include organic photo-sensitive materials having various advantages such as low costs, high productivities and low environmental pollutions have been prevailing.
Various types of organic photoconductors have been known, including photoconductive resin type photoconductors represented by polyvinylcarbazole (PVK), charge transfer complex photoconductors represented by polyvinylcarbazole-2,4,7-trinitrofluorenone (PVK-TNF), and function-separated type photoconductors utilizing a charge generating substance and a charge transporting substance in combination. Particularly, function-separated, laminate type photoconductors are being given much attention.
The organic photoconductors of function-separated type with high sensitivities, when used in the Carlson process, generally have disadvantages including that they have a low ability to be electrified, a poor ability to maintain surface charge (high dark attenuation) and, in addition, such abilities decrease greatly in repeated use, with the result that uneven density and/or fogging occurs in images obtained and contamination tends to occur in the case of a reversal development system.
In order to obviate the aforementioned disadvantages, use has been made of an interlayer between an electroconductive substrate and a photosensitive layer. This interlayer serves as a subbing layer for the photosensitive layer. For example, provision of a nylon type resin interlayer is disclosed in, for example, Japanese Patent Application Laying-Open No. 47344/1973, Japanese Patent Application Laying-Open No. 25638/1977, Japanese Patent Application Laying-Open No. 30757/1983, Japanese Patent Application Laying-Open No. 63945/1983, Japanese Patent Application Laying-Open No. 95351/1983, Japanese Patent Application Laying-Open No. 98739/1983 and Japanese Patent Application Laying-Open No. 66258/1985; provision of a maleic acid type resin interlayer is disclosed in Japanese Patent Application Laying-Open No. 69332/1974 and Japanese Patent Application Laying-Open No. 10138/1977; and provision of a polyvinyl alcohol resin interlayer is disclosed in Japanese Patent Application Laying-Open No. 105155/1983.
However, in many cases, the aforementioned subbing layer is made of an insulating resin, which increases the residual voltage of the photoconductor, and giving poor contrast in the image obtained. Although use of a polyamide resin (e.g., nylon) having a low electric resistance can suppress increase in the residual potential, a new problem arises in that variation of the properties of the photoconductor increases due to moisture in the environment because the polyamide resin has a high water absorption.